I'm just watching The Sopranos again (best serie ever) and there's an Ulver - Nattens Madrigal poster in the room of AJ. Amongst others of course and AJ wears shirts like Machine Head, Pantera, Slipknot (but it makes sense because they were very popular in the states back then). But I remember how surprised I was when I saw that Ulver poster.

IIRC there were other posters besides Ulver and they were all Century Media artists. Most likely someone on the show contacted CM to get posters for the set. A friend of mine was contacted in this manner for Dawsons Creek once.